/*
 * Copyright (C) 2011 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package org.ros.internal.node.topic;

import com.google.common.base.Preconditions;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * @author damonkohler@google.com (Damon Kohler)
 */
public class RepeatingPublisher<MessageType> {

  private static final boolean DEBUG = false;
  private static final Log log = LogFactory.getLog(RepeatingPublisher.class);

  private final Publisher<MessageType> publisher;
  private final MessageType message;
  private final int frequency;
  private final RepeatingPublisherThread thread;

  private final class RepeatingPublisherThread extends Thread {
    @Override
    public void run() {
      try {
        while (!Thread.currentThread().isInterrupted()) {
          publisher.publish(message);
          if (DEBUG) {
            log.info("Published message: " + message);
          }
          Thread.sleep((long) (1000 * (60f / frequency)));
        }
      } catch (InterruptedException e) {
        // Cancelable
      }
    }

    public void cancel() {
      interrupt();
    }
  }

  /**
   * @param publisher
   * @param message
   * @param frequency the frequency of publication in Hz
   */
  public RepeatingPublisher(Publisher<MessageType> publisher, MessageType message, int frequency) {
    this.publisher = publisher;
    this.message = message;
    this.frequency = frequency;
    thread = new RepeatingPublisherThread();
  }

  public void start() {
    Preconditions.checkState(!thread.isAlive());
    thread.start();
  }

  public void cancel() {
    Preconditions.checkState(thread.isAlive());
    thread.cancel();
  }

}
